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ARM: Tegra: DMA: Fail safe if initialization fails 

tegra_dma_init currently simply bails out early if any initialization fails.
This skips various data-structure initialization. In turn, this means that
tegra_dma_allocate_channel can still hand out channels. In this case, when
tegra_dma_free_channel is called, which calls tegra_dma_cancel, the walking
on ch->list will OOPS since the list's next/prev pointers may still be
NULL.

To solve this, add an explicit "initialized" flag, only set this once _init
has fully completed successfully, and have _allocate_channel refuse to hand
out channels if this is not set.

While at it, simplify _init:
* Remove redundant memsets
* Use bitmap_fill to mark all channels as in-use up-front, and remove
  some now-redundant bitmap initialization loops.
* Only mark a channel as free once all channel-related initialization has
  completed.

Finally, the successful exit path from _init always has ret==0, so just
hard-code that return. The error path still returns ret.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Colin Cross <ccross@android.com>
This commit is contained in:
Stephen Warren 2011-02-23 14:49:30 -07:00 committed by Colin Cross
parent ddb7d5d80e
commit ccac05152e
1 changed files with 10 additions and 12 deletions
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22
arch/arm/mach-tegra/dma.c
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@ -127,6 +127,7 @@ struct tegra_dma_channel {
#define NV_DMA_MAX_CHANNELS 32
static bool tegra_dma_initialized;
static DEFINE_MUTEX(tegra_dma_lock);
static DECLARE_BITMAP(channel_usage, NV_DMA_MAX_CHANNELS);
@ -352,6 +353,9 @@ struct tegra_dma_channel *tegra_dma_allocate_channel(int mode)
int channel;
struct tegra_dma_channel *ch = NULL;
if (WARN_ON(!tegra_dma_initialized))
return NULL;
mutex_lock(&tegra_dma_lock);
/* first channel is the shared channel */
@ -678,6 +682,8 @@ int __init tegra_dma_init(void)
void __iomem *addr;
struct clk *c;
bitmap_fill(channel_usage, NV_DMA_MAX_CHANNELS);
c = clk_get_sys("tegra-dma", NULL);
if (IS_ERR(c)) {
pr_err("Unable to get clock for APB DMA\n");
@ -696,18 +702,9 @@ int __init tegra_dma_init(void)
writel(0xFFFFFFFFul >> (31 - TEGRA_SYSTEM_DMA_CH_MAX),
addr + APB_DMA_IRQ_MASK_SET);
memset(channel_usage, 0, sizeof(channel_usage));
memset(dma_channels, 0, sizeof(dma_channels));
/* Reserve all the channels we are not supposed to touch */
for (i = 0; i < TEGRA_SYSTEM_DMA_CH_MIN; i++)
__set_bit(i, channel_usage);
for (i = TEGRA_SYSTEM_DMA_CH_MIN; i <= TEGRA_SYSTEM_DMA_CH_MAX; i++) {
struct tegra_dma_channel *ch = &dma_channels[i];
__clear_bit(i, channel_usage);
ch->id = i;
snprintf(ch->name, TEGRA_DMA_NAME_SIZE, "dma_channel_%d", i);
@ -726,14 +723,15 @@ int __init tegra_dma_init(void)
goto fail;
}
ch->irq = irq;
__clear_bit(i, channel_usage);
}
/* mark the shared channel allocated */
__set_bit(TEGRA_SYSTEM_DMA_CH_MIN, channel_usage);
for (i = TEGRA_SYSTEM_DMA_CH_MAX+1; i < NV_DMA_MAX_CHANNELS; i++)
__set_bit(i, channel_usage);
tegra_dma_initialized = true;
return ret;
return 0;
fail:
writel(0, addr + APB_DMA_GEN);
for (i = TEGRA_SYSTEM_DMA_CH_MIN; i <= TEGRA_SYSTEM_DMA_CH_MAX; i++) {